I once had (7) VMs on one host. But, coming originally from the mainframe world, I'm still haunted by the memory of when the mainframe went down, the entire company went down. I have now been using a one to one philosophy. I will say that I did think it was really cool to have multiple VMs running under one host, but my IT department were only ones who really appreciated it. The users just want uptime.

We all know that machines do crash and with my method, only one server goes down.

That depends entirely on your hosting setup. If your hosts don't have any sort of fail over, then
yeah, one host going down will kill everything. However, if your hosts aren't redundant, you're really leaving a lot of the benefits of virtualization untapped. Not only do you miss out on the automatic failover of a downed host, but you're going to have a crap ton of physical hardware to maintain.

Personally, we have three absolutely beastly VM Hosts. Each host is kept under 66% load, which means that if any one host fails, the other two will just pick up the VMs from the failed host. VSphere fails a VM over to another host so fast, that users might not even notice anything died.

For us, 40 VMs on three redundant VM Hosts is a hell of a lot easier and cheaper then 40 VMs on 40 VM hosts. I suppose that two VM hosts dieing would put a big cramp in our style, but if that happens it's probably because the server room just burnt down or got struck by lightning, in which case forty separate hosts wouldn't have helped any.

I have a "Utility" server that handles a number of different services. I used to have about 5 servers all doing the work that this one now does (not my design). As you said even though it's a VM and costs nothing (not really true... there is disk, CPU and RAM overhead) it still has to be managed. For me the deciding factor is simply what does the service do and can it be restarted without affecting anything. My Utility server handles Spiceworks, my AV management console, 3 different AD synch services and a few other processes. None of these interfere with each other and none are user facing so restarts for any reason at any time are possible.

Consolidation is just a bad technology loved by those who really don't understand it's dangers. Oh, It is certainly attractive to the inexperienced cheapskates.

Spend the money and have a single host for each VM.

I don't think that is what Dashrender was saying. I agree that having only one host is not a great idea but 1 to 1 is not needed. HA/Failover is dirt cheap/free compared to having a separate host for each VM.

I always limit it to one VM per host. This way you're not putting all of your eggs in one basket, which they call Consolidation.

I hope I'm not falling for a prank here, but as someone who is looking at doing a lot of virtualization over the next two years, I have to ask:

If limited to one VM per host, what are the advantages using VM's over sticking to physical? It seems to me this adds a layer of complexity for little or no benefit.

It is better because it allows you to migrate or restore a VMs to different hardware. But you can get automatic host failover on any virtual platform for cheaper than the cost of running one host per VM.

I always limit it to one VM per host. This way you're not putting all of your eggs in one basket, which they call Consolidation.

I hope I'm not falling for a prank here, but as someone who is looking at doing a lot of virtualization over the next two years, I have to ask:

If limited to one VM per host, what are the advantages using VM's over sticking to physical? It seems to me this adds a layer of complexity for little or no benefit.

It is better because it allows you to migrate or restore a VMs to different hardware. But you can get automatic host failover on any virtual platform for cheaper than the cost of running one host per VM.

But you can do that anyway (migrate VMs to other hardware). All you're doing by running one server per VM is increasing your cooling and electric bills.

If needed you can utilize both servers with HA and this will save you a lot. They are many HA solutions out there that are free or paid that you can look into if you are interested. With HA whenever you need to do a maintenance it will not be difficulty and also if one host dies the other takes over and no downtime. I have used Starwind vsan free and not that bad, if need you can get the paid one as well.

Bold

Thanks for reference! We're actually trying to help to ALL of our customers, it's just paid subscription what *guarantees* you support with SLA.

I always limit it to one VM per host. This way you're not putting all of your eggs in one basket, which they call Consolidation.

I hope I'm not falling for a prank here, but as someone who is looking at doing a lot of virtualization over the next two years, I have to ask:

If limited to one VM per host, what are the advantages using VM's over sticking to physical? It seems to me this adds a layer of complexity for little or no benefit.

It is better because it allows you to migrate or restore a VMs to different hardware. But you can get automatic host failover on any virtual platform for cheaper than the cost of running one host per VM.

But you can do that anyway (migrate VMs to other hardware). All you're doing by running one server per VM is increasing your cooling and electric bills.

Yes you're exactly right. I was not agreeing with the concept of running one VM per host. I was explaining that even in that scenario it is still best to virtualize.

I once had (7) VMs on one host. But, coming originally from the mainframe world, I'm still haunted by the memory of when the mainframe went down, the entire company went down. I have now been using a one to one philosophy. I will say that I did think it was really cool to have multiple VMs running under one host, but my IT department were only ones who really appreciated it. The users just want uptime.

We all know that machines do crash and with my method, only one server goes down.

How many servers do you have? There is no way we're buying 300 physical servers at over $1000 per server, plus the cost of licensing each one (I guess if I was going 1 to 1 I wouldn't use VMware), plus the cost of power, plus the cost of networking, plus the cost of a UPS to keep that amount of power running. I would call it being reasonable, not being a cheapskate. As long as there is a form of HA, or fault tolerance for the critical stuff, you're talking about a minute of downtime. That's assuming you're not load balancing or clustering.

I always limit it to one VM per host. This way you're not putting all of your eggs in one basket, which they call Consolidation.

Yikes. You're not really saving money hardware wise then. Why wouldn't you go to some type of clustering option like StarWinds VSAN or VMWare Vsan or any other hyperconverged solution. Less hosts with failover.

Actually, I make every new server its own host. This has a lot of advantages, including being able to remotely stop/restart the server, adjust RAM on the fly, recover the VM to new hardware, and much more.

This satisfies my need to have separate discreet servers, but still allows me to take advantage of the VM concept.

Sorry, but I've never entertained the thought of saving a little IT money by compromising hardware quality and dependability.

Actually, I make every new server its own host. This has a lot of advantages, including being able to remotely stop/restart the server, adjust RAM on the fly, recover the VM to new hardware, and much more.

You can do all of those things with any VM, on any host. Having just one VM per host changes none of these abilities.

Actually, I make every new server its own host. This has a lot
of advantages, including being able to remotely stop/restart the
server, adjust RAM on the fly, recover the VM to new hardware, and much
more.

This satisfies my need to have separate discreet servers, but still allows me to take advantage of the VM concept.

Sorry, but I've never entertained the thought of saving a little IT money by compromising hardware quality and dependability.

Depending on the exact scenario, it saves more than a "little" money. You can save a little money by shopping around for servers, you can save a boatload of money by using virtualization to its fullest. I also disagree that compromises hardware quality and dependability in any way. Honestly, I think even framing it that way is a disservice to anyone reading.

EDIT: For clarification purposes, I tried to make it less confusing that my comment was made to add on to what DragonsRule was saying but in response to what mtoddh commented previously.

How much electricity are you wasting and paying for by running all this mostly idle hardware?

Two key advantages of virtualization are making better use of your physical hardware resources and better fault tolerance.

Run a cluster of hosts connected to shared storage (NAS/SAN), dynamically move VMs around to balance out hardware resources and give yourself enough headroom to still run if one of the hosts went down.

I have worked in environments that ran 500+ VMs on 8 beefed up hosts in a cluster and everything ran fine.

With datacenter licensing, there was a dedicated VM for each application or role.

I think that there is a time and place for this. I have almost all of my VMs in a VMWare cluster, but I had an older server that was decently spec'd that I didn't want it to go to waste, so I installed VMWare on it and spun up a VM. By at least having the hypervisor on the host, it gives me the ability to easily add more VMs on it down the road, if needed.

I think that there is a time and place for this. I have almost all of my VMs in a VMWare cluster, but I had an older server that was decently spec'd that I didn't want it to go to waste, so I installed VMWare on it and spun up a VM. By at least having the hypervisor on the host, it gives me the ability to easily add more VMs on it down the road, if needed.

Yeah that makes sense, i would not recommend purposely designing it such where you still roll out a physical box for every server you want to run. But if you do need to run a single server for something it should still be virtualized to make the VM hardware independent for DR and migration purposes.

Actually, I make every new server its own host. This has a lot of advantages, including being able to remotely stop/restart the server, adjust RAM on the fly, recover the VM to new hardware, and much more.

This satisfies my need to have separate discreet servers, but still allows me to take advantage of the VM concept.

Sorry, but I've never entertained the thought of saving a little IT money by compromising hardware quality and dependability.

If one of your 1-to-1 hosts fails or needs to be taken down for maintenance, can you at least roll it's VM over to another host?

If not, you're actually loosing dependability. If one of our clustered hosts goes down or needs scheduled maintenance, the VMs just automatically fail over to another host and continue to run. With a High Availability cluster and automatic fail over, you can have physical hosts straight up die and your VMs' up time is not affected. Even if you had one host in the cluster for each VM, you'd gain that benefit.

Actually, I make every new server its own host. This has a lot of advantages, including being able to remotely stop/restart the server, adjust RAM on the fly, recover the VM to new hardware, and much more.

This satisfies my need to have separate discreet servers, but still allows me to take advantage of the VM concept.

Sorry, but I've never entertained the thought of saving a little IT money by compromising hardware quality and dependability.

But why even adjust RAM with only one VM? Then it's the decision to use the installed RAM or not to use it. In that case could also plug the RAM out and save it for needed time. Ok then you cant adjust the RAM any more. But if you only run 1 VM i don't see the point, to give the machine it maximum installed power. But i don't get the 1 vm per host philosophy any way.

Actually, I make every new server its own host. This has a lot of advantages, including being able to remotely stop/restart the server, adjust RAM on the fly, recover the VM to new hardware, and much more.

This satisfies my need to have separate discreet servers, but still allows me to take advantage of the VM concept.

Sorry, but I've never entertained the thought of saving a little IT money by compromising hardware quality and dependability.

How do you figure you would only save a 'little' money over your limit of 1 VM per host?

If you have to have 10 Hosts for your !0 VMs instead of 2 or 3 hosts for 10 VMs then your Hardware costs are 7-8 times higher, as are your ongoing Power and cooling costs. There could also be rather significant additional licensing costs for Hypervisor, backup software... Your reliability is lower than 2 or 3 hosts in a HA Cluster as well.

You really aren't taking advantage of the VM concept at all as the point of the VM concept is to more fully utilize each servers resources *and* increase reliability by eliminating a single port of failure. You have accomplished neither in your situation.